Ceramic dielectric compositions

ABSTRACT

The ceramic dielectric materials of the present invention consist of a ternary solid solution CaTi03-PbTi03-La203.2Ti02 and CaTiSiO5, a part of which forms a solid solution with the said ternary system. The said ceramic materials are suitable as temperature compensating capacitors.

United States Patent [72] Inventors Tsunehiko Yoshioka;

I-llshashi Sato; Naoki Suda, all of Akita-ken, Japan [21 Appl. No. 778,415

[22] Filed Nov. 25, 1968 45] Patented Nov. 23, 1971 [73] Assignee TDK Electronics Co., Ltd.

Tokyo, Japan [32] Priority Aug. 29, 1968 1 1 J p n [54] CERAMIC DIELECTRIC COMPOSITIONS [56] References Cited UNITED STATES PATENTS 2,220,774 11/1940 Navias 106/39 3,427,173 2/1969 Fujiwaya et al... 106/39 3,431,124 3/1969 Hayashi et a1. 106/39 3,440,067 4/1969 Fujiwara et a1. 106/39 FOREIGN PATENTS 1,134,783 1 1/1968 Great Britain 106/39 Primary Examiner-Robert D. Edmonds Anorney-Wenderoth, Lind & Ponack ABSTRACT: The ceramic dielectric materials of the present invention consist of a ternary solid solution CaTi0 -PbTi0 La 0 and CaTiSiO a part of which forms a solid solution with the said ternary system. The said ceramic materials are suitable as temperature compensating capacitors.

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CERAMIC DIELECTRIC COMPOSITIONS The present invention relates to ceramic dielectric materials suitable for use as temperature compensating capacitors.

The well known system CaTiO -CaTiSi an equimolar D, E and F in the ternary diagram of FIG. 4.

It is necessary to control the amount of CaTiSiO; included in the solid solution CaTiSiO -CaTiO -PbTio -La OfiTio to achieve favorable dielectric and ceramic properties. It is mixture in which the components form separate domains 5 somewhat difficult to restrict the overall amount of CaTiSiO; without forming a solid solution, exhibits typically the followuniquely on the basis of dielectric characteristics but since, in i h i i 2; Q =2,5 )0 d T C -O p.p.m./C. a certain range, the characteristics can be kept constant over a Because of the fact that they do not form a solid solution, it is range of CaTisiOs M11011"t y Controlling the composition not feasible to obtain a Q-value higher than 2,500 and, aaa a' zi it is advantageous {0 (ha moreover, it is necessary to keep the firing temperature within 10 amount of CaTisiOa to a range from 40 to 85 mo] P a narrow range to achieve sufilcient maturity. fYVhTn ti? agount exceeds 85 m Percent, it becomes It is the fundamental object of the present invention to proqfit g z '?g l gg? ?a gggeg as an in rediem of the f mater'als .o'values solid s lu on CaTiSiO -CaTiO -PbTiO -La O52TiO can be abput demandmg less Severe fir.mg condmfms and 3p 5 controlled by means of adjusting the amount of La O '2TiO,. as tempmfmre F' f such In the solid solution CaTiO ,,,-La,O -2TiO the amount of materials can be obtained by the comblnatlon of CaTlSlO and La 0 2Tio cannot exceed 20 mo percent The inclusion of a solid solution consisting of to 95 mol percent of CaTiO a in eicess of 40 mo] percent results poor mproduci l to 2 9 pemem of PbTlo and 1 to mo] percent of bility of dielectric characteristics due to irreproducible loss of Lazoa. 21.102 20 PbTiO caused by vaporization in the process of firing.

In the Present mvenuon the Propomon of For the better understanding of the present invention, some posely rather large so that a part of it fon'ns a solid solution examples are given in the following with the system CaTi0,,-PbTiO -La O -2Tio thus leading to a system consisting of two separate phases CaTiSiO and EXAMPLE 1 CaTiO -PbTiO -L O -2Ti0 -CaTiSiO It should be noted that the s: g i l or ca-risioy Presintered materials of chemical Pure grade, according to CaTiO La,0,-2Ti0,, czi'risio does not form a solid solution the by with the other components. Therefore, it is of essential importance that both l l ri0 and l.si,0 -2Tio be included. misc: "'3'? In making a ceramic composition according to this inven can), 21 tion, the raw materials are first presintered and ground to a PbTiOs 6 fine powder separately. Calcium titanate-silicate (CaTiSiO Lapanno 3 calcium titanate (CaTi0 and lanthanum titanate (La oy 2TiO are presintered at or below l,250 C. in an oxidizing Z gfs 'sgggg 22 3321 32 13 2 5 25 5 atmosphere while lead titanate (PbTiO is presintered at or 3 5 dished Sha e and than fired to maturity at a emture of below 900 C. also in an oxidizing atmosphere. After cooling, 1 to 1 3 C in oxidizin atmos here (air) p each of the presintered materials is ground to a fine powder, cenlmic y thus pf exhibits following and then the several powders are mixed according to desired characteristics composition. To the mix, there is added a suitable binding agent, e.g., polyvinyl alcohol, the mixture pressed into shape 40 and then fired to maturity at a temperature of l,250 to 1,300 of 73 C. in an oxidizing atmosphere. dielectric constant The present invention is characterized by a solid solution of C) P-P-"'- the following composition: o'value 4 CaTiO, 45 to 95 mol percent me u e at l MC,S 25 C. zi giz ri f mo percent l to 20 mol percent The dielectric characteristics of a number of different compositions according to the present invention produced by the to which is added CaTiSiO a part of which forms a solid soluprocedures described in the above example are shown in the tion with the said ternary solid solution. following tabulation. The measurements were made at 1 Referring to the accompanying drawings:

7v TABLE Composition (mol percent) Characteristics Dielectric Temperature Specimen Lai0i constant Q-value coefficient, No. CaTiSlO CaTiO; PbIiOs 2Tl0 at 25 C. at 25 p.p.m./ C.

What is claimed is: 1. A ceramic dielectric material useful for temperature compensating capacitors consisting of a ternary system 5 CaTiO -PbTiO -La O -2TiO and CaTiSiO in an amount between 40 and mol percent the said ternary system consisting of 45 to mol percent CaTiO l to 40 mol percent PbTiO and 1 to 20 mol percent La O -2TiO- 

